Wednesday, February 28, 2007

No Doughnuts

Tonight Pete revealed something to us. Something disturbing. There can be no doughnuts. Fortunately, it is not as bad as it sounds. He was referring to polygons in the older ARC coverage files. A doughnut in this sense of the word is when you have a polygon object, but there is an area inside that polygon that has different attributes. For example, a city may have an area within it's larger boundaries that is not incorporated by the city. That is the hole in the doughnut. The coverage files apparently had a lot of trouble with these. The later shapefiles and geodatabases are totally cool with doughnuts though.

Over there on the right is an example of some of our exercising tonight. It was about association tables to each other and to spatial data. Pete had a good example of a desire to make a campus map showing which buildings were served by which security guards. In this example, there was some map data of the campus, and the chief of security guards also had a spreadsheet with a list of his officers and which buildings they covered. So then we related those 2 datafiles and were able to automatically generate the map showing the buildings and the names of the security guards for each and even color coded them by security officer.

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